1. Field of the Invention
The present invention generally relates to a backlight module and, more particularly, to a direct type backlight module.
2. Discussion of the Related Art
Most liquid crystal display (LCD) devices are passive devices in which images are displayed by controlling an amount of light input from an outside light source. Thus, a separate light source (for example, backlight module) is generally employed for irradiating an LCD.
Generally, backlight modules can be classified into an edge type or a direct type based upon arrangement of lamps within the device. The edge type backlight module has a lamp unit arranged at a side portion of a light guiding plate for guiding light. The edge type backlight modules are commonly employed in small-sized LCDs due to their lightweight, miniature and low electric consumption. However, the edge type backlight modules are not suitable for large-sized LCDs (20 inches or more). A direct type backlight module has a plurality of lamps arranged in regular positions to directly illuminate an entire surface of an LCD panel. The direct type backlight modules have higher utilization efficiency of light energy and longer operational service life than the edge type backlight modules, and are specially produced for large-sized LCD devices.
One kind of direct type backlight module is illustrated in FIG. 1. The backlight module 100 includes a plurality of spacers 11, a plurality of light sources 12, a frame 13 and a diffusion sheet 14. The frame 13 includes a plane substrate (not labeled), a number of circumferential sidewalls (not labeled) extending from the substrate to a predefined opening (not labeled), and a reflective film (not shown) that is coated in an inner surface of the frame 13. The diffusion sheet 14 is accommodated in the opening of the frame 13. The spacers 11 are disposed in the space encompassed by the diffusion sheet 14 and frame 13 for supporting the diffusion sheet 14. The light sources 12 are arranged in the substrate of the frame 13 with a selected interval.
In the current backlight module 100, the reflective film coated in the frame 13 reflects the light scattered downwardly from the light sources 12 upwardly to the diffusion sheet 14. Because the brightness is in an inverse ratio to the distance, the diffusion sheet 14 right above the light sources 12 will have more light beams and more brightness, while the other portions of the diffusion sheet 14 above the left and right sides of the light sources 12 will have less light beams and less brightness. Thereby lowering the light uniform of the direct backlight 100, causing irregular shade brightness on the LCD. Furthermore, the backlight module 100 employs a plurality of light sources 12 to reach a high luminance, these light sources 12 produce a great deal of heat accumulated inside the backlight module 100. Therefore, heat dissipation of the backlight module 100 is usually a hard nut to crack.
Therefore, a new direct type backlight module is desired in order to overcome the above-described shortcomings.